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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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pedrocols
wgallupe
LeGrace
Kentley
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Jim McShane
eickmewg
Dahlberg
peterh
Dave_in_Va
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BNR_1
Bob Latino
17 posters

    12AU7 type tubes .. Great driver tubes for tube audio amps ...

    Dahlberg
    Dahlberg
    Dahlberg


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    • Post n°26

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    Post by Dahlberg Wed Jan 25, 2017 7:46 pm

    I like the RCA 5963's a lot. They have great tone and that they
    are missing a little of what's the RCA 12au7 clear tops strong
    suit might not be that important after all.

    Anyone who has an idea of what's the expected run in time for the Tungsol 12au7's ?

    Edit: Never mind, I found this comment on Tubes Asylum from some guy.

    Earnie3 wrote:PS when I first put them in they were a little warmed over lack luster and bass was loose. I gave them about 50hrs and they turned to a whole different animal...

    So I'm leaving them in for the rest of the week, at least Cool
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    Dahlberg
    Dahlberg
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    • Post n°27

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    Post by Dahlberg Fri Jan 27, 2017 11:09 am

    And ~20 hours later  Shocked  Shocked Twisted Evil Very Happy Cool
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    Falcon4646
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    Falcon4646


    Posts : 12
    Join date : 2010-02-21
    • Post n°28

    12AU7 type tubes .. Great driver tubes for tube audio amps ... - Page 2 Empty 12AU7 Tube Types

    Post by Falcon4646 Sun Feb 19, 2017 8:14 pm

    Bob;

    So you have gone away from the 12BH7s for the M-125s. When I purchased my M-125 kits in 2011 the 12BH7 was recommended and I went with matched low-noise Electro-Harmonix tubes.

    Now looking at 12AU7 Cryo tubes from Cryoset Certified. See: http://www.cryoset.com/catalog/index.php?cPath=21_44&osCsid=3a8e7adfab422524f90195c74e0f0d60

    What 12AU7 source would you recommend?

    Also, have noticed lately when I shut down M-125s I can hear speaker white noise from what sounds like capacitive discharge. Should I be concerned?

    Thanks in advance!
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    Bob Latino
    Bob Latino
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    • Post n°29

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    Post by Bob Latino Sun Feb 19, 2017 8:37 pm

    Falcon4646 wrote:Bob;

    So you have gone away from the 12BH7s for the M-125s. When I purchased my M-125 kits in 2011 the 12BH7 was recommended and I went with matched low-noise Electro-Harmonix tubes.

    Now looking at 12AU7 Cryo tubes from Cryoset Certified. See: http://www.cryoset.com/catalog/index.php?cPath=21_44&osCsid=3a8e7adfab422524f90195c74e0f0d60

    What 12AU7 source would you recommend?

    Also, have noticed lately when I shut down M-125s I can hear speaker white noise from what sounds like capacitive discharge. Should I be concerned?

    Thanks in advance!

    You can use EITHER 12AU7 type tubes or 12BH7 tubes as driver tubes in any of the VTA amps. Some people like 12BH7 tubes because they are a little taller than a 12AU7 - maybe the "bigger is better" theory in action here ... Actually I now feel that there isn't a whole lot of difference in sound quality between the 12AU7 type tube or a 12BH7 in these amps. Right now I am using a Mullard 12AU7 in the front position and a GE 12BH7 in the rear position of my own M-125 amps. I like the way the amps sound set up this way at least in my own music system. You have to realize that different people have different ways that they want their music system to sound. The nice thing about 12AU7's is that there are still many USA made 12AU7's and military/industrial 12AU7 types (5963, 5814 and 6189) still in existence. You can many times pick up from Ebay and other online internet tube vendors quality USA made (RCA, GE and Sylvania) versions of this tube at reasonable prices.

    Most readers of this forum now know that the FRONT tube on the VTA M-125's and the CENTER tube on the VTA ST-70/ST-120 is the single tube that you can change out that will usually show some sound difference in the amp(s).

    Capacitive discharge does occur when you shut the amps OFF. The components within the amp will look at progressively lower operating voltages. Sometimes you may get a funny noise from a tube when it is faced with an operating voltage well below what the tube is supposed to see. This is not harmful to the amp ..

    Bob
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    jimmytamp
    jimmytamp
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    Join date : 2013-06-24
    • Post n°30

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    Post by jimmytamp Wed Feb 22, 2017 4:54 am

    You can use EITHER 12AU7 type tubes or 12BH7 tubes as driver tubes in any of the VTA amps. Some people like 12BH7 tubes because they are a little taller than a 12AU7 - maybe the "bigger is better" theory in action here ... Actually I now feel that there isn't a whole lot of difference in sound quality between the 12AU7 type tube or a 12BH7 in these amps. Right now I am using a Mullard 12AU7 in the front position and a GE 12BH7 in the rear position of my own M-125 amps. I like the way the amps sound set up this way at least in my own music system. You have to realize that different people have different ways that they want their music system to sound. The nice thing about 12AU7's is that there are still many USA made 12AU7's and military/industrial 12AU7 types (5963, 5814 and 6189) still in existence. You can many times pick up from Ebay and other online internet tube vendors quality USA made (RCA, GE and Sylvania) versions of this tube at reasonable prices.

    Most readers of this forum now know that the FRONT tube on the VTA M-125's and the CENTER tube on the VTA ST-70/ST-120 is the single tube that you can change out that will usually show some sound difference in the amp(s).

    Capacitive discharge does occur when you shut the amps OFF. The components within the amp will look at progressively lower operating voltages. Sometimes you may get a funny noise from a tube when it is faced with an operating voltage well below what the tube is supposed to see. This is not harmful to the amp ..

    Bob    [/quote]

    Bob,


    Just to reconfirm that on VTA120, I can change the Centre tube to 12BH7 while the L&R will use 12AU7, and this will be applicable as well for the other way round (12BH7 on L&R, 12AU7 on C)?


    Thanks,

    Jimmy
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    Bob Latino
    Bob Latino
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    • Post n°31

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    Post by Bob Latino Wed Feb 22, 2017 6:43 pm

    Yes - The center tube may be either a 12AU7 type tube or a 12BH7 tube. The two side tubes may also be either 12AU7 or 12BH7 but both side tubes should be of the same type.

    Bob
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    jimmytamp
    jimmytamp
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    • Post n°32

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    Post by jimmytamp Thu Feb 23, 2017 4:56 am

    Thanks, Bob.

    Cheers,
    Jimmy
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    bluemeanies
    bluemeanies
    bluemeanies


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    Join date : 2015-02-09
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    Location : Folsom Pa.
    • Post n°33

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    Post by bluemeanies Thu Feb 23, 2017 10:06 pm

    pedrocols wrote:I just purchased a matched pair of Raytheons 12au7(pretty cheap). To my ears they do have good bass and not too busy on the higher frequencies.  Definitely less roll of than the Mullard cv4003. Midrange however is very good.  I like them!


    I thought that driver tubes were specifically for the high end and mid-range rather than the low end.
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    jimmytamp
    jimmytamp
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    • Post n°34

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    Post by jimmytamp Mon Feb 27, 2017 3:28 am

    I just rolled my driver tubes on ST120 in triode-mode: NOS Raytheon 5814 on both sides + EH 12Bh7 in centre. I got clearer bass (not boomy) and the mid range bigger, sound-stage seems closer especially for female vocals. The highs is less harsh than before when I used NOS Philip on both sides.I mostly listen to acoustic jazz, and now I can hear the player's fingers on his upright bass. But with Philips, I could hear more on 3D sound stage.
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    jimmytamp
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    • Post n°35

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    Post by jimmytamp Mon Feb 27, 2017 3:31 am

    jimmytamp wrote:I just rolled my driver tubes on ST120 in triode-mode: NOS Raytheon 5814 on both sides + EH 12Bh7 in centre. I got clearer bass (not boomy) and the mid range bigger, sound-stage seems closer especially for female vocals. The highs is less harsh than before when I used NOS Philip on both sides.I mostly listen to acoustic jazz, and now I can hear the player's fingers on his upright bass. But with Philips, I could hear more on 3D sound stage.


    My previous set was NOS Philips 12AU7 on both sides + NOS Raytheon 5814 in centre.

    Now, I like this new set than before.


    Regards,
    Jimmy
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    Bob Latino
    Bob Latino
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    • Post n°36

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    Post by Bob Latino Mon Feb 27, 2017 10:13 am

    Just to make clear that Jimmy's amp dates from July of 2013 and is fully broken in .. You should not tube roll in a NEW AMP. As the amp breaks in, the sound will change slightly for the first 200 hours or so. After 200 hours .. maybe 3 hours a day for a couple of months, the sound will stabilize and you can tube roll if you want. I recommend just rolling the center tube in the VTA ST-70 and ST-120 or just the front tube in the M-125 monoblocks. This tube has more influence on the sound of the amp than any other tube in the amp .

    Bob
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    jimmytamp
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    • Post n°37

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    Post by jimmytamp Mon Feb 27, 2017 1:16 pm

    Bob Latino wrote:Just to make clear that Jimmy's amp dates from July of 2013 and is fully broken in .. You should not tube roll in a NEW AMP. As the amp breaks in, the sound will change slightly for the first 200 hours or so. After 200 hours .. maybe 3 hours a day for a couple of months, the sound will stabilize and you can tube roll if you want. I recommend just rolling the center tube in the VTA ST-70 and ST-120 or just the front tube in the M-125 monoblocks. This tube has more influence on the sound of the amp than any other tube in the amp .

    Bob


    Yes, and 4 years later my ST120 is still working in good condition. The same with my VTA-SP12R/PH12, since 2014 and till now is still running well.

    Thanks for the very well built amp & pre-amp, Bob & Roy.

    Cheers,

    Jimmy
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    tubenutr
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    • Post n°38

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    Post by tubenutr Mon Feb 27, 2017 4:54 pm

    Never really warmed up to the 12bh7.
    Tried numerous types and nah.....
    Put a mullard 12au7 in the center and 2 EH 12au7s on the sides. Very good, open
    sound that pleases my ear. Go figure.
    Just my humble opinion.

    Mike
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